The best thing you can do is stop snacking if you snack.
Eat three meals a day. For now, cut out all processed foods - biscuits, low fat yoghurts, crisps and savoury snacks. Just eat home made food. The main reason for this is that processed foods can trigger massive cravings that are not real hunger but feel like it.
Don't 'diet' for now. Just focus on healthy eating. That means protein at every meal, plenty of veg - go for 8 portions of fruit and veg a day - 3 of fruit and 5 of veg.
Increase your lean protein intake. It really does keep you full for longer - eggs, chicken, lean red meats, white fish, grilled back bacon etc.
Move. The brilliant thing about being very overweight is you are a walking gym. Every time you move you are doing a serious weight lifting challenge.
Sounds daft but last year I realised what the best exercise in the world is - it's squats. The reason is, they train the muscles that lift the bum from the seat so they encourage you to jump up more. Doorbell rings - you jump to get it. Phone rings, same. Kids shout, you jump to find them instead of hollering from the sofa. Squats make you more active. Start today with a solid upright chair, just get up from it and sit down in it without stopping as many times as you can. Tomorrow do one more etc. Increase by one each day until you can do forty so easily it's not an issue. Then do squats without the chair!
Add simple movements to everyday tasks - do sumo squats while cleaning teeth or just shimmy or windmill your arms while waiting for the kettle to boil.
You will get results quickly.